-- o ICOM

em
Table 2: Frequency Dependent Values
30 Meters 40 Meters
Cl.3 150 pF 200pF
C5.7 270pF 470 pF
C6 560pF 1000 pF (equals O.()()1mF)
L1 27 turns. 1'26 wire, T-50-6toroid 34 lums.1'26 wire. T-50-6 I0r0id
L3.4 12turns.I2:2.T-S0-2 14 lurns.I2:2.T-50-2
LS 34tums.128 Of 30. T-50-6 50 lurns, 128 or 30, T-50-6
L6 45 tums.128 Of 30, T-50-6 451ums.128 Of 30, T-50-2
C188
Radio Shack 272-1437 (22 pFJ
These parts must be obtained from either Radiokil, Circuil Specialists.
Of Mouser (e~cept Cl88).
1.5. prevent this problem.
RF Amp: This device amplifies the incoming
recei ved signals to give the receiver a
lillie more punch and better signal-to-noise
ratio.
Mixer: The mixer is a doubly -bala nced
mi xer using the common l N4148 or lN9l4
d iode , The di ffere nce bet ween the antenna-s
sig nals and the VFO's frequency yields the
audio frequency appearing at the speaker.
This is the mosl fea rsome looking pa rt of the
circuit . It is actually the most fun to build.
Audio C hain: The preamp, Q8 , in conjunction
with U3 , amplifies the audio to listening
level. The audio filler U2 is a low-pass
filter of conventional design. It cuts off at
approximately 700 Hz.
Some Sim ple Rules of Heme-bee..'"
You can build this project quickly and easily
if you observe a few simple rules that are
common to any hobby or craft. These are
absolutely indispensable:
eK now the rig. Study the schematic and plans
very thorou ghly . Be familiar with the modules
and know what they are designed to
accomplish.
-Know the parts. Be fam iliar with what parts
make up the project. Study the parts placement
guide. Figure 4 , and match the flow of
th e ci rcuitry against the parts placement
guide. Also. remember that you ca n destroy a
part by reversi ng polarities, etc.
-0 0 slowly! This one piece of advice will
save you hours of teeth-gritting tension and
frustration later. There is no exception to th is
rule.
-00 methodically. Build this project moduleby-module,
where possible. This will help 10
prevent many possible problems and will enhance
the learning potential of this project.
,
'. 3. ~ TW'STEO
TOGET"ER
er PER 'HC"~
, ,
,
•
•
•
Modular Approach
.- Pflu"p
FRO"
~,F.O,
? '~ .
O rder of
Constr uction
Do not be afra id to
etch a single- or double-sided
c ircuit
board yourself. Copy
the foil pattern (Figure
5) directly onto
Tech-2oo film (Tech­
200 is supplied by the
Meadowlake Corp.,
PO Box 497. Northport
N Y 11 7 6 8 ) ,
which is etch-resistant. o r pu rchase supplies
from Radio Shack. Otherwise, get a circuit
board from a supplier. (Midland Technologies,
34374 E. Frontage Road , Bozeman MT
59715,406-586- 1190. Contact is Lee
Leste r. Double-sided tinned PC board, pr ice
$ 12.50 plus shipping and handling .) There
are also a limited number of complete parts
kits available, including p ri nted circuit
board. (Tanner Electronics, 130 1 w est Bellline
Road. Ca rrollton TX 7.5